In recent years, daily discomfort caused by irritable sensation, such as an increase in hypersensitivity such as allergy due to an increase in exogenous stimulants such as chemical substances or house dust, which is caused by changes in the living environment, or a rise in the tendency of disliking foul odors of the living environment, including one's body odor and various living odors at homes, has been a problem.
Senses can be classified into somatic senses such as cutaneous sensation and deep sensation; visceral senses such as visceral pain; and special senses such as visual sensation, auditory sensation, gustatory sensation, and olfactory sensation. The sensory information is, for example, received by peripheral sensory receptors such as various receptors of the skin, muscle spindles, retina, olfactory mucosa, taste buds, and the hair cells of cochlea, converted to nerve impulses during sensory perception, and then transmitted to the sensory center as electric signals.
For example, the sensation of pain is induced by noxious stimuli (a temperature stimulus, a chemical stimulus, and a mechanical stimulus) received at the free nerve endings of the skin. In a free nerve ending, ion channels that are respectively sensitive to each of various stimuli are present, and when stimulated, these ion channels are opened, and thereby cation channels flow into the cell. Consequently, potential-dependent cation channels are activated, and an action potential (impulse) of the nerve is generated (Non-Patent Document 1). Furthermore, stimuli that are known to cause itchiness include physical stimuli such as mechanical stimuli, heat stimuli, and electrical stimuli, and chemical stimuli such as pruritogenic substances. It is speculated that these stimuli cause histamine to be released mainly from the mast cells in the dermis, and the released histamine binds to the receptors on the free nerve endings and causes an inflow of calcium ions, thereby finally generating an action potential of the nerve (Non-Patent Document 2).
Similarly, for the generation of any other sensation, the information is transmitted to the sensory center in the form of an action potential that is generated by the activation of potential-dependent cation channels of neurons. Furthermore, potential-dependent cation channels participate not only in such generation or transmission of the action potential, but also in the release of neurotransmitters at the synaptic clefts or the neuromuscular endings.
Therefore, if the activation of a potential-dependent cation channel is inhibited, sensation can be suppressed. In fact, methods for suppressing sensation by using a potential-dependent cation channel inhibitor have been traditionally used at medical sites and the like. For example, lidocaine (for example, Xylocaine (registered trademark)), which is used as a local anesthetic or an antiarrhythmic, is a potential-dependent sodium channel inhibitor. Gabapentin (for example, Gabapen (registered trademark) or Neurontin (registered trademark)), which is a potential-dependent calcium channel inhibitor, is used as an anticonvulsant or an adjuvant analgesic. Furthermore, it has been reported that an inhibitor of a potential-dependent calcium channel or a potential-dependent sodium channel (for example, Varapamil) increases the tolerance threshold of the skin against external aggression, and can be applied to hypersensitivity of the skin (Patent Document 1).
When a potential-dependent cation channel of the sensory nerves is inhibited, not only a sensory suppression effect for medical purposes may be obtained, but also there is a possibility that the quality of life can be improved by suppressing or controlling the irritable feeling or unpleasant feeling that is felt in everyday life.
Particularly, there is a demand for a masking material that can be used for the purpose of suppressing unpleasant odors of foods, pharmaceuticals, cosmetics, household commodities and the like, or for deodorization of objects.
Thus, there have been attempts to search for substances which have a strong ability to inhibit the ion channels of olfactory cells, as masking materials of unpleasant odors, by utilizing the mechanism of action of human olfactory CNG channel proteins (Patent Document 2).
However, a satisfactory masking material for unpleasant odors has not yet been obtained.
Meanwhile, adamantane derivatives have unique properties such as high heat resistance, transparency, chemical resistance, and lubricating properties, and are widely used particularly as photoresist materials. By taking advantage of these characteristics, adamantane derivatives are also used as dental compositions (Patent Document 3).
However, it is not known that adamantane derivatives have a potential-dependent channel inhibitory action or an unpleasant odor masking effect.